A. Field of the Invention
The present invention relates generally to capacitor discharge ignition systems and more paritcularly to an improvement in component packaging and coil arrangements of a capacitor discharge ignition system.
B. Description of the Prior Art
Various capacitor discharge systems of the prior art have been developed to provide a breakerless ignition system for the control of an engine whereby an appropriately timed signal is supplied to the primary winding of an ignition coil to induce a high voltage in a secondary winding of the ignition coil to fire a spark plug or spark plugs associated with the engine.
The capacitor discharge systems of the prior art utilize various circuit arrangements and coil arrangements including triggering and charging coils in combination with a rotating permanent magnet on the engine flywheel to induce voltage in a charging coil, charge a capacitor with the induced voltage and discharge the capacitor into the primary winding of an ignition coil. Such arrangements are shown for example in U.S. Pat. No. 3,941,111 which issued to T. F. Carmichael on Mar. 2, 1976; U.S. Pat. No. 4,056,088 which issued to T. F. Carmichael on Nov. 1, 1977; U.S. Pat. No. 4,036,201 which issued to B. O. Burson on July 19, 1977; and co-pending application Ser. No. 14,141 filed on Feb. 22, 1979 by Ronald J. Kiess.
A capacitor discharge ignition system manufactured by Wabash, Inc., the assignee of the present application, is illustrated in FIGS. 1 and 2. Briefly, the capacitor discharge ignition system includes an auxiliary winding 2 wound on a widened base section 4a of a coil support 4. A primary winding 6 of an ignition coil is wound on a narrowed upstanding section 4b of the coil support 4 with the primary winding 6 above the auxiliary winding 2. Various circuit components are disposed and mounted about the primary winding 6. A secondary winding 8 of the ignition coil is disposed over the circuit components and the primary winding 6.
The completed assembly as shown in FIG. 2 is enclosed in a cup-shaped housing and potted. The various electrical connections generally referred to at 9 are utilized to connect the capacitor discharge ignition system to the engine to be controlled.
As shown in FIG. 2, various circuit components of the capacitor discharge ignition system are mounted within the capacitor discharge housing assembly. However, due to packaging efficiency requirements as dictated by engine design and OEM specifications, some circuit components, such as a charging capacitor 7 are mounted externally to the overall capacitor discharge ignition housing assembly and connected to the other circuit components by one of the leads of the cable connections 9. The high tension secondary connector 5 is shown in FIGS. 1 and 2 for connection to a spark plug through a suitable cable.
While the above-described capacitor discharge ignition system of FIGS. 1 and 2 is generally suitable for its intended purpose, it would be desirable to increase the packaging efficiency of capacitor discharge ignition systems in order to either reduce the overall volume thereof or provide additional integrated circuit components while maintaining or improving operational characteristics. The reduction in overall volume of the capacitor discharge ignition system housing is beneficial to allow reduced overall size of the apparatus incorporating the engine such as small and lightweight chain saws or power mowers. Further, it is also advantageous to incorporate all circuit components of the capacitor discharge ignition system within a sealed housing enclosure for ease of assembly, long life and desirable operating characteristics.
The capacitor discharge ignition system disclosed in U.S. Pat. No. 4,036,201 utilizes a relatively large E-shaped core in a cup-shaped housing to mount the circuit components of the capacitor discharge ignition system. The cup-shaped housing includes an ignition coil with primary and secondary windings as shown in FIG. 3 with the overall diameter of the ignition coil being substantially less than the diameter of the cup-shaped housing. The auxiliary coil is mounted above the ignition coil and as illustrated in FIG. 3 therein is of smaller diameter than the ignition coil with substantial amounts of free volume space within the cup-shaped housing. Electrical circuit components of the capacitor discharge ignition system are mounted about the ignition coil and between the ignition coil and the cup-shaped housing. The arrangement of FIG. 3 does not appear to be designed for maximum volumetric efficiency in packaging of the capacitor discharge ignition system but instead appears to be based on the required dimensions of the E-shaped core. Thus, the capacitor discharge ignition system of U.S. Pat. No. 4,036,201 exhibits large, unused volumetric space within a housing and is not designed for maximum space efficiency and minimum size of the overall capacitor discharge ignition system housing assembly.
While the above-described capacitor discharge ignition systems of the prior art are generally suitable for their intended use, it would be desirable to provide a capacitor discharge ignition system with optimum volumetric space utilization while minimizing the overall dimensions of the capacitor discharge ignition system housing and while maintaining desired operational characteristics.